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New Member

1G port

We're running Blade Centers with CISCO modules in them and ran into a problem with the uplink ports...

The 4 uplink ports (10/100/1000)were configured to auto/auto and, so were the ports (10/100/1000)on the upstream 3750 switch that the uplink ports were connected to. The negociated speed ended up being 1000Mb/s...So we tried to hardcode the speed to 1000Mb/s on the uplink port, while theauto/auto setting on the upstream switch was left intact (auto/auto). That resulted in traffic through the uplink ports coming to a halt. When we change the setting back to auto/auto, traffic started going again...

New Member

Re: 1G port

Sorry, quick trigger....The question that I have is why would the uplink ports stop working when the speed was hardcoded to 1000Mb/s?


New Member

Re: 1G port

I have never tried this with trunks, but I know for a fact if you do this w/ workstations you'll end up with a duplex mismatch. I have found it's best practice to leave trunk ports set at Auto/Auto and hardcode access ports where possible (Printers, Workstations, etc).

New Member

Re: 1G port

Adam, thanks for your reply. These uplink ports are access ports, not trunk - I should have mentioned it in my original message. On a typical Cisco switch, I would always hardcode the duplex & speed settings, however these Blade Centers are counter-intuitive and, for some reason, will only work when set to auto/auto...

Hall of Fame Super Silver

Re: 1G port


I do not have experience with this particular combination so can not speak from experience. But I do know that if one side is set for auto and the other side is hard set then the negotiation will fail and the auto side will assume some default value. I am guessing that the uplink that is set for auto has a default it will take when negotiation fails. And I suspect that the default speed for the uplink speed is not the same as what you hard coded on the downstream. So you have two devices trying to communicate on different speeds. Result = no communication.

I believe that the basic principle is: if one side is set for auto then both sides should be set for auto. The default behavior when the other side is not negotiating may be hard to predict.



New Member

Re: 1G port

Hi ,

It is no matter that whether it is a uplink port / normal switch port, If port of the one switch is set to 'auto' then other side (remote end port) should be configured as 'auto' otherwise negotiation will fail.

Orelse If we set one side as '1000' then we should manually set the remote side also as '1000' . (Because In most of the swithes default speed is 'auto')

If one side is 'Auto' and remote end is '1000' then connection will fail.

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